MEMS-based optical image stabilization

Abstract

In one example, a camera is provided that includes: a plurality of MEMS electrostatic comb actuators, each actuator operable to exert a force on at least one lens; and an optical image stabilization (OIS) algorithm module operable to command the plurality of actuators to actuate the at least one lens responsive to motion of the camera.

What is claimed is: 
     
       1. A camera, comprising:
 a plurality of integrally formed electrostatic actuators, each actuator configured to exert a force on at least one lens, wherein each actuator comprises a fixed portion, a movable portion configured to move, relative to the fixed portion, between a first position, in which the actuator is operable, and a second position, in which the actuator is non-operable, and a latch configured to latch the movable portion in the first position; 
 an optical image stabilization (OIS) algorithm module configured to command the plurality of actuators to actuate the at least one lens responsive to motion of the camera; and 
 a driver integrated circuit operable to drive the actuators responsive to the OIS algorithm module's commands. 
 
     
     
       2. The camera of  claim 1 , wherein each actuator is configured to exert a tangential force on the at least one lens, and wherein the OIS algorithm module is configured to command the plurality of actuators to tangentially actuate the at least one lens responsive to the motion of the camera. 
     
     
       3. The camera of  claim 2 , further comprising:
 a plurality of position sensors corresponding to the plurality of actuators, each position sensor measuring a tangential displacement of its corresponding actuator; and 
 a translator module operable to translate the tangential displacements from the position sensors into a displacement for the lens, wherein the OIS algorithm module is also responsive to the lens displacement. 
 
     
     
       4. The camera of  claim 1 ,
 wherein the OIS algorithm module is integrated in the driver integrated circuit, wherein the OIS algorithm module is configured to command the driver integrated circuit to apply an acceleration pulse to the movable portion to latch the movable portion in the first position. 
 
     
     
       5. The camera of  claim 1 , further comprising:
 an imager configured to digitize an image taken through the at least one lens; and 
 an image processor integrated circuit operable to process the digitized image, wherein the OIS algorithm module is integrated in the image processor integrated circuit. 
 
     
     
       6. The camera of  claim 1 , wherein the camera is integrated into a cellular telephone. 
     
     
       7. The camera of  claim 6 , wherein the actuators are electrostatic comb actuators. 
     
     
       8. The camera of  claim 7 , further comprising:
 a circular stage to receive the at least one lens, wherein the plurality of actuators comprises three actuators symmetrically disposed outside of the circular stage. 
 
     
     
       9. The camera of  claim 1 , wherein the OIS algorithm module includes a Kalman filter for predicting an intended motion of the camera. 
     
     
       10. The camera of  claim 9 , further comprising:
 a gyroscope, wherein the gyroscope measures a pitch and yaw of the camera, and wherein the Kalman filter predicts an intended motion of the camera based the measured pitch and yaw, 
 wherein the OIS algorithm module is configured to command the plurality of actuators to actuate the at least one lens based on a difference between the intended motion of the camera predicted by the Kalman filter and an unintended jittering motion of the camera. 
 
     
     
       11. The camera of  claim 1 , wherein the OIS algorithm module commands the plurality of actuators based upon a relatively low data rate, and wherein the camera further includes at least one controller for controlling the actuators at a relatively high data rate based upon the OIS algorithm module commands. 
     
     
       12. A method of image stabilization, comprising:
 sensing a motion of a camera using a gyroscope; 
 based upon the sensed motion, determining a desired lens actuation that stabilizes a camera lens; 
 translating the desired lens actuation into desired tangential actuations; 
 tangentially actuating the lens using a plurality of tangential actuators according to the desired tangential actuations; 
 moving a movable portion of each of the plurality of tangential actuators to be latched at a first position, in which the tangential actuator is operable to actuate the lens, before tangentially actuating the lens; 
 filtering sensed camera motion from the gyroscope to provide a prediction of an intended position for the lens; 
 sensing tangential actuations by the plurality of tangential actuations; 
 translating the tangential actuations into a current lens position; and 
 subtracting the current lens position from the intended lens position to provide a lens position error due to unintended camera motion, wherein the desired lens actuation stabilizes the lens by addressing the unintended camera motion. 
 
     
     
       13. The method of  claim 12 , wherein the filtering is a Kalman filtering. 
     
     
       14. The method of  claim 12 , wherein the filtering is a high pass filtering. 
     
     
       15. The method of  claim 12 , wherein the tangential actuation is a MEMS electrostatic comb tangential actuation, and wherein the movable portion of each of the plurality of tangential actuators is moved to the first position by applying an accelerating pulse to the movable portion to cause a lever of the movable portion to engage a latch. 
     
     
       16. A system, comprising:
 a lens; 
 a stage holding the lens within a curved aperture; 
 three integrally formed tangential actuators symmetrically disposed about the stage, each tangential actuator operable to displace the stage in a direction tangential to a curve defined by the curved aperture, wherein each tangential actuator comprises a fixed portion, a movable portion configured to move, relative to the fixed portion, between a first position, in which the tangential actuator is operable, and a second position, in which the tangential actuator is not operable, and a latch configured to latch the movable portion in the first position; 
 an optical image stabilization (OIS) algorithm module operable to derive an actuation command for each of the three tangential actuators responsive to motion of the camera; and 
 a driver integrated circuit operable to drive the actuators responsive to the OIS algorithm module's commands. 
 
     
     
       17. The system of  claim 16 , wherein the curved aperture is a circle and the curve defined by curved aperture is a circle. 
     
     
       18. The system of  claim 16 , further comprising three V-shaped flexures corresponding to the three tangential actuators, wherein each tangential actuator couples to the stage through the corresponding V-shaped flexure. 
     
     
       19. The system of  claim 18 , wherein each V-shaped flexure has a longitudinal axis aligned in the direction tangential to the curve.